We, as growers, know the fact that overwatering the plants in the soil will probably drown them. We have also known that hydroponics replace the soil with water. These facts have got me wondering how does hydroponics not drown plants, especially when the plant roots are in water all the time?
So how does hydroponics not drown plants? Hydroponics system does not drown plants because it contains an air pump. Air pumps help keep the nutrient solution oxygenated by the air bubbles; this way, the roots will still be in the water all the time and safe from any drowning.
Let’s take a step back to the elementary school where we first knew about how plants live. Plants’ leaves undergo a photosynthesis process in the presence of sunlight. It uses this sunlight to convert water and carbon dioxide into oxygen and energy that can be either stored or used for growth.
Roots, on the other hand, are entirely different than leaves. While a plant’s leaves use photosynthesis to produce energy, plant roots undergo a respiration process. They use oxygen and glucose, that is translocated from the leaves, to undergo respiration and produce energy. This energy is used by the root cells for the uptake of nutrients from the soil. As a consequence, water follows the nutrients to the roots using the osmosis process. I know it’s a little bit of science. But I believe that every hydroponic grower is a newbie scientist in his small lab which is his growing room.
What Happens In Soil VS Hydroponics
Plants in soil drown when being overwatered by growers for some time. Most growers got anxious about their plants not getting enough water, so they keep overwatering them until it’s too late. When plants are overwatered, the air pockets between the surrounded soil get destroyed. Therefore, the only source of oxygen is gone, which leads to roots being unable to do respiration to produce energy for nutrient uptake. Moreover, there will be no more water uptake; this leads to stunted growth of wilted leaves.
Not only does the nutrient and water uptake slow down, but also fungi will start growing on roots. When roots got submerged, oxygen levels decrease and moisture increases, this is the perfect environment for fungus to grow. Phytophthora, Pythium, and Rhizoctonia are three different genera of fungi that grow over submerged roots and cause root rot.
Usually, root rot will cause some changes in the root’s appearance. In hydroponics, the root’s color is white. There can be some stains from the nutrient solution, but that is ok. Root rot will change the root’s color to brown, grey, and even black.
When using hydroponics, the way things work is different. Root has to be placed in water for the uptake of nutrients to take place; this can create room for root rot and plant drowning to take place, which is why air pumps are used. Air pumps produce air bubbles continuously, which oxygenate water constantly. Despite the high moisture that is present around the roots, the high oxygen levels will prevent any fungi from growing.
However, water levels must not be high enough that it submerges the whole root length. Half of the root’s length is more than enough for the plant to have a healthy nutrient and water uptake. If the water levels are high, root rot can happen. Although it is easier to identify in hydroponic plants than soil plants, no one would like to see their plants drowning from some silly mistakes.
The Kratky Method
The Kratky method was first discovered and named after Bernard Kratky, who is a researcher at the University of Hawaii. It was first published in 2009 in a journal called Actae Horticulture. I believe that this method is widely adopted by growers, it can revolutionize the way we grow plants due to its direct effect on electricity consumption.
The basic theory of the Kratky method is that you leave at least half of the root’s length suspended in air and not submerged in the nutrient solution. The plants then will develop what is called air roots or oxygen roots. Air roots absorb oxygen from the surrounded air rather than from the nutrient solution. With the continuous oxygenation of the roots, root cells can undergo regular respiration to produce energy for nutrient uptake. Moreover, high oxygen levels will limit any growth of opportunistic fungus.
Some growers have used this method to delete air pumps from their systems. Removing air pumps didn’t affect their crops as there is another source of oxygen that the roots can reach out to. By eliminating air pumps, growers have obtained much lower electricity bills, which in turn, improved the economic viability of their crops; This can significantly affect and boost the profit of growers who are growing plants with reduced economic viability like hydroponic rice.
You can also use this method with an air pump. It can help you as a spare method in pump malfunction or unaccounted power outs. But remember, you have to keep the air roots suspended in the air. If your plant developed air roots and then you submerged them again in the nutrient solution, there will be a high chance of root rot for your plant due to drowning.
How To Treat Root Rot If Happened?
You have to decide if the plant is worth saving or not. Some plants are present in multiple bucket systems like recirculating DWC, which makes it more difficult to stop the system and try to keep the plant. The rot stage is important. Also, it depends on the crop type. Growing plants like tomatoes could be worth it. Saving a tomato tree can help you save time on growing a new one. On the other hand, If you are growing nine lettuce heads on a single floating raft, it will not be probably worth it to stop the entire system for only one head.
You also have to determine the stage of rot. The healthy roots color in hydroponics is white. The nutrient solution can stain it, but the primary color is white, which is entirely different than roots in the soil. Dirt and maybe ground insects will stain soil roots. Hydroponic rotten roots will look brown, grey, or even black with a distinct smell. You must detect the level of rot spread among the root and identify it its savable or not.
You can remove the lettuce head and try and diagnose the cause of the root rot. There are different causes of root rot to happen. You have to check them and detect the right reason to eliminate them and prevent any future root rotting from happening.
The nutrient solution level can be too high. As you know, at the beginning of the article, high water levels can make your plant drown, which in turn, causes root rot. You have to ensure that the water levels are not too high so that the plant will not drown.
You can also check the air bubbles. Air pumps might not deliver the right amount of air bubbles that oxygenate the solution enough for the roots to undergo respiration. But be careful of the number of bubbles produced. If the number of bubbles is too high, it might raise the water level that soaks the Rockwool in the net pot. A lot of new growers found their hydroponic plants drowning without knowing that their Rockwool is soaked, which causes their plants to suffocate and drown.
Check also the temperature of the nutrient solution. High temperatures might not drown your plants, but inevitably it will cause root rot and promote fungal growth.
The nutrient solution can be the original cause of infection of the root rot without you knowing or taking notice. More often, growers will ignore and leave some plant debris or leave remains in the nutrient solution. These remains will be the perfect medium for fungal and bacterial growth. I think that this cause is the most dangerous one. Your entire hydroponic system can get infected in no time, and you would not even notice the original reason. And it will not take too long for your whole system to get affected by root rot.
Follow the below steps to remove root rot from your hydroponic system:
Decrease the growing lights of your hydroponic system. By lowering the lights, you will slow down the photosynthesis process that is done in the leaves. So the water uptake is also decreased. You have to do this step because the drowned roots cannot withstand the normal water uptake of the plant in normal light conditions.
Remove the plant from the system and wash its roots under running water. Remove any rotten root or debris using scissors.
Drain the whole nutrient solution of your system. Start sterilizing and removing any debris in the base of the container. You can use alcohol for sterilization but make sure the container is dry before adding the new nutrient solution.
Add beneficial bacteria to your system. Beneficial bacteria will compete with the fungus on food sources. Therefore, limiting the fungal growth and at the same time have no harmful effect on the plant roots.
Add the air pump to the system. Make sure that the air stones are well distributed in the system and that it produces sufficient air bubbles to keep the solution oxygenated. Moreover, try to keep the nutrient solution temperature constant at 65-degree Fahrenheit.
How To Protect Your Plant From Getting Drowned?
Having a spare air pump can be a life savior for your plants. My air pump has got malfunctioned continuously. Lucky for me, most of the time was easy for me to go out and purchase a new one as they were during working hours. But I wouldn’t forget one time when the air pump failed at 11 pm. During this time almost all of the stores were closed, and if I ordered one online, it would not arrive before two days. Before reaching the sunset, the plant’s leaves got wilted and were in a seriously lousy condition. Moreover, if you are in an area with continuous power outages, I advise you to get a small generator that can run your system for a few hours as an emergency plan.
Try to keep your nutrient solution level low; This will help your plant to develop air roots to absorb the oxygen from surrounded air. By using the Kratky method with an air pump, the Kratky way acts as a plan B for your roots in case of insufficient oxygen supply.
You have to make sure also that the air bubbles are not too high that it reaches the Rockwool. Soaking the Rockwool is very dangerous and can drown your plants easily even if the water level is not too high. Most newbies fall in this pit. They keep wondering why their plants are wilted when the water level is not too high, and they forget that the Rockwool is soaked, which will suffocate the plant’s roots without you even noticing.
Can you overwater in hydroponics? Yes, overwatering can happen in hydroponics. It usually occurs when there is an imbalance between the amount of sunlight and water that the plant is receiving.
Why don’t roots rot in hydroponics? Root rot happens in hydroponic plants if the water level is too high that it causes the plants to drown. It has a lower risk in hydroponics than in soil because most soil growers tend to water their plants more often due to that they are anxious that their plants aren’t receiving enough amount of water.